1. Field of the Invention
The present invention relates to multi-layer fullerenes and a method of manufacturing the same. More particularly, the present invention relates to multi-layer fullerenes having a cage-inside-cage structure in which fullerenes having different carbon numbers are nested, and a method of manufacturing the multi-layer fullerenes.
2. Description of Background Art
A C60 fullerene was discovered in 1985. A C60 fullerene is a carbon cluster having a molecular structure shaped like a soccer ball. Since then, many studies have been conducted on carbon compounds having a polyhedral structure, and various types of fullerene compounds have been discovered.
Fullerene compounds are spherical carbon compounds containing only carbons. Higher fullerenes such as a C60 fullerene having 60 carbon atoms and fullerenes having an even carbon number of more than 60 are collectively called fullerene compounds. Examples of such higher fullerenes include a C70 fullerene, C80 fullerene, C120 fullerene, and the like. A C180 fullerene, C240 fullerene, C560 fullerene, or the like is considered to exist in theory.
Application of such fullerene compounds has been studied. For example, substances in which a C60 fullerene is doped with an alkaline metal have attracted attention as a new functional material because of their superconductivity. In particular, application of such substances to electronic materials has been extensively studied.
Conventionally, fullerene compounds are manufactured using a laser vaporization method or arc discharge method. In the laser vaporization method, for example, a gas flow containing a carbon source such as hydrocarbons and a photosensitizer is irradiated using a strong laser beam. This causes the carbon source to thermally decompose to produce black amorphous soot as a reaction product. Xiang-Xin Bi, P. C. Eklund, et al. have reported that spherical amorphous nanoparticles with an average particle diameter of 300 xc3x85 were found in a pyrolyzed product of benzene obtained using an iron carbonyl as a catalyst (J. Maste. Res., 10, 2875 (1995)). J. V. Weber et al. have reported that a fullerene compound having a small carbon number is reconstructed into a fullerene compound having a large carbon number by heating soot produced using an arc discharge method at a high temperature (J. Anal. Appl. Pyrolysis, 29, 1 (1994)). However, details of the reaction mechanism are unknown at present.
Accordingly, an object of the present invention is to provide multi-layer fullerenes with a novel structure which has unknown characteristics in addition to those of conventional fullerene compounds and are expected to be applied to various fields, and a method of manufacturing the multi-layer fullerenes.
As a result of extensive studies to achieve the above objects, the present inventors have found that fullerenes having different carbon numbers can be obtained by heating a carbon-containing substance at a temperature of 2300xc2x0 C. or higher in the presence of a C60 fullerene. This finding has led to the completion of the present invention.
Specifically, the present invention provides the following multi-layer fullerene and a method of manufacturing the multi-layer fullerenes.
(1) A multi-layer fullerene comprising a C60 fullerene enclosed in a C240 fullerene.
(2) A multi-layer fullerene comprising a C240 fullerene enclosed in a C560 fullerene.
(3) A multi-layer fullerene comprising a C80 fullerene enclosed in a C240 fullerene which is enclosed in a C560 fullerene.
(4) A substance comprising at least one of the multi-layer fullereness according to the above (1) to (3).
(5) A method of manufacturing a multi-layer fullerene comprising heating carbon-containing substances at a temperature of 2300xc2x0 C. or higher in the presence of a C60 fullerene.